The invention relates to making stator flaps for a turbomachine, in particular to making flaps having a variable setting angle, and to installing them in a turbojet inlet casing.
In conventional manner, stator flaps comprise a vane-forming portion of aerodynamic profile which is provided at two opposite ends with fastening pieces which, for flaps of variable setting angle, form pivots in radial alignment.
It is known that vanes can be made of composite material by shaped draping of plies of fiber reinforcement. The draping can be performed on a piece constituting a former. The plies are impregnated with resin before or after draping. After polymerization enabling the resin to harden, a blank is obtained of a shape that is close to that of the vane that is to be made. The blank is then machined to its final dimensions.
Compared with a metal vane, a vane made of composite material provides a significant saving in weight while conserving very good mechanical behavior. Nevertheless, a problem which arises is making the connection with the fastening portions. The known solution which consists in localized draping of the vane reinforcing plies around metal fastening portions can be unsatisfactory, with the connection being made fragile by the forces to which the vane is subject being concentrated since they need to be taken up by the fastening portions.
An object of the invention is to propose an architecture for a turbomachine stator flap that makes it possible in particular to resolve the above-mentioned problem of transmitting forces to the fastening portions.
According to the invention, this object is achieved by a stator flap including a structural beam comprising a structural core for the vane and formed integrally with at least a fraction of the fastening portions, the structural core being surrounded by a composite envelope forming at least the aerodynamic profile of the blade.
The invention is remarkable in particular for separating the structural function which is provided by the structural beam and the aerodynamic function which is provided the vane envelope. The structural continuity between the vane core and the fastening portions ensures that the forces applied to the vane are transmitted directly without any risk of delamination between the vane and the fastening portions.
The structural beam is advantageously made of a composite material. It could be made of metal.
According to a feature of the stator flap of the invention, at least one of the fastening portions is provided with a metal band which, when said fastening portion constitutes a pivot, is prevented from rotating relative to the fastening portion about the pivot axis.
According to another feature of the stator flap, it has internal passages opening out firstly at one end of at least one fastening portion and secondly along at least one of the edges of the vane.
Such stator flaps provided with internal passages can advantageously be installed in a turbomachine inlet casing surrounded by a defrosting manifold, the attachment portions into which the internal passages of the flaps open out then being implanted in the inlet casing in the defrosting manifold so as to cause it to communicate with said internal passages.
The invention also seeks to provide a method of making a stator flap as defined above. According to the invention, such a method comprises the steps consisting in:
making a structural beam comprising a structural core of the vane formed integrally at least with structural cores of the fastening portions; and
draping fiber reinforcement plies around the structural beam so as to make a composite envelope surrounding the structural core of the vane and forming at least the aerodynamic profile of the vane.